a <a href="#Run_time_panics">run-time panic</a> occurs.
In other words, even though the dynamic type of <code>x</code>
is known only at run time, the type of <code>x.(T)</code> is
known to be <code>T</code> in a correct program.
</p>

<pre>
var x interface{} = 7          // x has dynamic type int and value 7
i := x.(int)                   // i has type int and value 7

type I interface { m() }

func f(y I) {